1. Field of Invention
This invention relates in general to production of oil and gas wells, and in particular to a hanger lockdown tool that also functions as a fluid pumping sub.
2. Description of Prior Art
Tubing, casing or other hangers, annulus seals and other wellhead assembly or well completion components are typically rigidly locked into the bore of the wellhead assembly or into any other receptacle in which they are landed with a lockdown mechanism, to ensure safe operating conditions. One such lockdown mechanism includes an activator ring that is set in an annulus formed between a hanger and an inner surface of a bore through the wellhead assembly. A lockdown ring which is coaxial with the activator ring generally has a profile surface that mates with profiles in the inner surface of the bore of the wellhead assembly. The activator ring urges the lockdown ring radially outward against the inner surface of the bore of the wellhead assembly. The mating of the profiles of the lockdown ring and the inner surface of the bore maintains the hanger in position within the wellhead assembly.
During fluid pumping operations while drilling and production fluids are pumped into the well through the wellhead, vibrations can cause the wedged activator ring to work loose, allowing the lockdown ring to disengage from the profiles of the wellhead assembly. This can occur, for example, during cementing operations. In order to prevent the loss of lockdown capability, traditionally, a specialty tool such as a threaded keeper ring can be screwed into the wellhead assembly to hold the activator ring in place before the fluid pumping sub is lowered into the wellhead assembly. The fluid pumping sub is a generally annular member that inserts into the wellhead assembly and whose lower end mates with an upper end of the hanger located within the wellhead assembly. However, installing a keeper ring requires an extra trip into the well as well as the time-extensive process of the removal of the blowout preventer, in order to provide access for the keeper ring to reach the activator ring.